Enamines and enamides are useful synthetic intermediates of use to the agrochemical, pharmaceutical, and other fine chemical industries. Previously, enamine and enamide compounds have been prepared by: a) addition of amine or amide to an epoxide followed by dehydration; b) direct addition of --NH-- containing compounds to alynes; c) Curtius reaction of .alpha., .beta.-unsaturated azides; or d) Beckmann rearrangement of .alpha., .beta.-unsaturated oximes. Each of these methods requires several synthetic steps for the synthesis of enamides or enamines and some suffer from lack of regiospecificity.
Prior to the instant invention, it was known in the art that Cu(I) compounds could be used as stoichiometric reagents to effect the coupling of aryl bromides and --NH-- containing compounds. This chemistry was extended to vinyl bromides by Ogawa et al (Ogawa, T.; Kiji, T.; Hayami, K.; and Suzuki, H.; Chemistry Lett. 1991, p. 1443) who reported the coupling of vinyl bromides with the potassium salt of an acidic amide in the presence of a stoichiometric amount of copper iodide to provide enamides.
The coupling of aryl halides and an --NH-- containing compound has also been accomplished catalytically using a base and a palladium (Pd) catalyst. This catalyst system, however, is not known or reported to couple vinyl halides and --NH-- containing compounds. Kosugi, M.; Kameyama, M.; and Migita, T.; Chem Lett., 1983, p. 927 reported the Pd catalyzed coupling of tin amides and aryl halides to form aryl amines. Several other references have disclosed the Pd catalyzed coupling of amines and aryl halides in the presence of a strong base to form aryl amines (e.g., see Paul, Frederic; Patt, Joe; and Hartwig, John F.; J. Am. Chem. Soc., 1994, 116(13), pp. 5969-70; Louie, Janis; and Hartwig, John F.; Tetrahedron Lett., 1995, 36(21), pp. 3609-12; Hartwig, John F.; and Paul, Frederic; J. Am. Chem. Soc. 1995, 117(19), pp. 53734; Wolfe, John P.; and Buchwald, Stephen L.; J. Org. Chem., 1996, 61(3), pp. 1133-5; Guram, Anil S.; Rennels, Roger A.; and Buchwald, Stephen L.; Angew. Chem., Int. Ed. Engl., 1995, 34(12), pp. 1348-50).
A. J. Arduengo, et al., J. Am. Chem. Soc., vol. 113, p. 361-363 (1991) and A. J. Arduengo, et al., J. Am. Chem. Soc., vol. 114, p. 5530-5534 (1992) report the synthesis of (1,3-disubstitutedimidazol-2-ylidene) carbenes.
The present invention provides for the use of a nickel catalyst complex rather than the more expensive palladium catalysts of the prior art and allows for the one step coupling of vinyl halides in addition to aryl halides. Other objects andadvantges of the present invention will become apparent to those skilled in the art upon reference to the detailed description which hereinafter follows.